Among patients 75 years and older dizziness is the most common presenting complaint in a doctor's office. Although pathophysiological changes have been identified in the vestibular system of aged animals and humans, the role of these changes in the production of dizziness and dysequilibrium is unclear. The proposed research will use modern quantitative techniques to assess the function and morphology of the peripheral and central vestibular systems in olderly normal subjects and patients complaining of dizziness. Specific aim 1 is to quantify vestibular function in two groups of elderly persons: a group complaining of dizziness and a group without symptoms of dizziness. All subjects will undergo baseline testing (including history questionnaires and quantitative tests of balance and visual-vestibular interactions) and yearly repeat examinations. The goals are to define the natural history of common vestibular disorders in older patients and to quantify changes in vestibular function that normally occur with aging. Specific aim 2 is to identify pathology in the peripheml and central vestibular systems in the patient group. The goals are to determine the accuracy of the clinical diaposes, to clarify the pathophysiology of common vestibular disorders and to search for pathology in patients with dizziness of unknown cause. Specific aim 3 is to perform quantitative studies of the morphology of the peripheml and central vestibular systems in both groups of elderly persons. The goal is to achieve a quantitative correlation of function with morphology. Examination of the temporal bone and brain of normal subjects and patients who have undergone quantitative visual-vestibular function testing is the unique feature of this stidy. Prior clinical- pathological studies of the vestibular system have relied on meager clinical information and no quantitative data. This multidisciplinary study can overcome these limitations and thereby improve the diagnosis and management of elderly persons complaining of dizziness.